T 1.5 - 1.9 Flashcards
1
Q
Physical processes that volcanoes cause
A
- lava flows
- pyroclastic flows
- ash falls
- gas eruptions
- secondary hazards - lahars, jökulhlaup
2
Q
What are lava flows and how are they caused?
A
- molten magma on the earths surface is so hot, it flows
- viscosity determined by the amount of silicon dioxide
- buildings can be burnt and covered if it is running
- 1977: lake wall collapsed and lava drained in 1 hr, across 9km, swallowing villages while people were asleep
3
Q
Gas steam emissions from volcanic eruptions:
A
- h20 vapour: rainfall events, then potentially lahars
- steam escapes though geysers
- so2 forms very fine particles that get into the stratosphere, also causes acid rain which corrodes buildings and affects vegetation
- fluorine gas is poisonous in high conc. and contaminated farmland or water supply
4
Q
What are pyroclastic flows and how are they caused?
A
- frothing bubbles of molten magma in the vent, burst explosively to eject a dense mixture of hot gases and pyroclastic material, eg glass, pumice, ash
- can reach temperatures of up to a 1000
- move rapidly down side of volcano up to 700km/h
- leave behind volcanic deposits ( can dam rivers)
5
Q
How are ash falls caused and what are they?
A
- carried into the atmosphere, potentially even trans boundary
- most fall locally, causing roofs to collapse, breathing difficulties for people and animals, bury crops
- disrupts flights paths of planes
6
Q
How are lahars caused and what are they?
A
- water mixed with volcanic deposits, flowing rapidly along existing valleys
- could be caused by heavy rain, or maybe volcanic ash has has created humid air, condensation, clouds and rain
- very fast (60kmh) carry large amounts of material
7
Q
Impacts of Mountain Nyiracongo eruption
A
- major eruptions in 1977, 2002, 2021
- 2km wide continuous lava lake
- responsible for 40% of Africa’s volcanic eruptions
- shield volcano
2002 - 147 killed, 400k evacuated
8
Q
Eykafjallajokull eruption 2010
A
- single eruption divided into many phases
- 14th April, relatively explosive eruption (4 on VEI)
- situated 200m under glacial ice, where melt water caused two things: rapidly vaporising water, rapid lava cooling created cloud of abrasive glass rich ash
- but deaths = 0
9
Q
Social/ human impacts of Eykafjallajokull eruption
A
- cancelled sports, music and arts events
- localised health effects around south Iceland due to abrasive ash
- increased regional traffic for land based travel
- cancelled/postponed political events
10
Q
Economic impacts of eykafjallajokull eruption
A
- European economy lost 5 billion
- African economies lost as much as 65 million
- loss for airlines ($1.1 billion)
- knock on effect from cancelled events (eg, MotoGP in Japan)
11
Q
Regional significance of eykafjallajokull eruption
A
- ash cloud reached as far as northern Italy, meaning any flights to and from Europe were affected
- increased in land based travel so train prices and road traffic rose
- however reduced air and noise pollution recorded around Europe
12
Q
Global significance of eykafjallajokull eruption
A
- Japan MotoGP suffering
- Kenyan flower industry lost 2 million
- New Zealand fish farmers still were winners as they could have more domestic demand
13
Q
Land use zoning
A
- keeping residential and commercial zones away from active dormant volcanoes
- easier with shield volcanoes
- hard because of soi fertility
14
Q
Hazard resistant design
A
- retrofit buildings
- cross bracing
but this is expensive on a national scale and requires government legislation
15
Q
Engineering defences
A
- sea walls and mangroves to absorb wave energy
- back up utility plans for hospitals and police stations
- drain craters to prevent lahars
